This invention relates to a dry cell of the kind having a zinc electrode in the form of a sleeve or canister.
Known dry cells of the Leclanche kind have the disadvantage that leakage of electrolyte tends to occur for the following reason: With a known Leclanche dry cell having a cylindrical zinc canister as the anode and an electrolyte which consists mainly of ammonium chloride, the zinc of the anode, upon battery discharge, decomposes and zinc chloride is deposited on the side wall of the zinc canister and in its vicinity. At the same time fine zinc di-ammonium chloride crystals form which slowly develop to a semi-transparent layer on the surface of the zinc. This semi-transparent layer produces, due to the difference of density between the anode side of the zinc chloride and the cathode side, an osmotic pressure and allows liquid to pass from the electrolyte to the zinc anode wall.
The positive ions, such as zinc ions and zinc ammonium ions, due to the action of the electro-osmotic pressure, are attracted to the zinc anode. The zinc of the anode is decomposed by the discharge and becomes thinner. The zinc produces, due to its decomposition, a thick zinc chloride layer which dissolves the starch and fabric in the gummed paper which separates the anode and the electrolyte and the filterability of the electrolyte paste is promoted.
In the known Leclanche dry cell, for this reason, the liquid of the paste moves, due to osmotic pressure and the electro-osmotic pressure, to the zinc anode and rises between the thinned zinc sheet and the gummed layer of the separator, the liquid of which has now become too concentrated, and deposits on the upper surface of the depolarizer. The manganese dioxide of the depolarizer loses, in the meantime, its oxidization effect and the remaining anode zinc produces hydrogen gas which drives the liquid electrolyte through the pores into the outer casing, thereby causing the leakage of the electrolyte.
The provision of a thick zinc canister and a thick solid seal for the outer casing cannot in themselves prevent leakage of the electrolyte. In order to exclude the leakage of the electrolyte it is necessary to prevent completely the pressing out of the electrolyte onto the upper face of the cathode depolarizer.